[CmdletBinding(SupportsShouldProcess = $true)]
param(
  [Parameter(Mandatory = $true)]
  [string]$BackupPath,

  [string]$ApplicationPoolName = 'XiaoshuLegacySync',
  [string]$PhysicalPath = 'C:\inetpub\xiaoshu-sync',
  [Parameter(Mandatory = $true)]
  [string]$HealthUrl
)

$ErrorActionPreference = 'Stop'
Set-StrictMode -Version Latest

function Assert-Administrator {
  $identity = [Security.Principal.WindowsIdentity]::GetCurrent()
  $principal = [Security.Principal.WindowsPrincipal]::new($identity)
  if (-not $principal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    throw '请使用“以管理员身份运行”的 PowerShell 执行回滚。'
  }
}

Assert-Administrator
Import-Module WebAdministration

$resolvedBackupPath = (Resolve-Path -LiteralPath $BackupPath).Path
if (-not (Test-Path -LiteralPath (Join-Path $resolvedBackupPath 'Xiaoshu.LegacySyncBridge.dll'))) {
  throw '回滚目录不是有效的同步桥备份：缺少 Xiaoshu.LegacySyncBridge.dll。'
}
if (-not (Test-Path "IIS:\AppPools\$ApplicationPoolName")) {
  throw "IIS 应用池不存在：$ApplicationPoolName"
}

$timestamp = Get-Date -Format 'yyyyMMdd-HHmmss'
$failedPath = "$PhysicalPath.failed-$timestamp"

if ($PSCmdlet.ShouldProcess($PhysicalPath, "从 $resolvedBackupPath 回滚小树旧系统同步桥")) {
  Stop-WebAppPool -Name $ApplicationPoolName -ErrorAction SilentlyContinue
  if (Test-Path -LiteralPath $PhysicalPath) {
    Copy-Item -LiteralPath $PhysicalPath -Destination $failedPath -Recurse -Force
    Remove-Item -LiteralPath $PhysicalPath -Recurse -Force
  }
  New-Item -ItemType Directory -Path $PhysicalPath -Force | Out-Null
  Copy-Item -Path (Join-Path $resolvedBackupPath '*') -Destination $PhysicalPath -Recurse -Force
  & icacls.exe $PhysicalPath /inheritance:r /grant:r "SYSTEM:(OI)(CI)F" "Administrators:(OI)(CI)F" "IIS AppPool\${ApplicationPoolName}:(OI)(CI)RX" /T /C | Out-Null
  Start-WebAppPool -Name $ApplicationPoolName

  $healthy = $false
  foreach ($attempt in 1..12) {
    try {
      $health = Invoke-RestMethod -Uri $HealthUrl -Method Get -TimeoutSec 10
      if ($health.status -eq 'ok' -and $health.service -eq 'xiaoshu-legacy-sync' -and $health.version -eq 'v1') { $healthy = $true; break }
    } catch {
      Start-Sleep -Seconds 2
    }
  }
  if (-not $healthy) {
    throw "文件已回滚，但健康检查没有通过：$HealthUrl。当前失败版本保存在 $failedPath。"
  }

  Write-Host "同步桥回滚完成：$resolvedBackupPath"
  Write-Host "回滚前版本保留在：$failedPath"
}